I have found decent free content via some channels via my Rokus. But... you can get unlimited streaming for about $10/month from Netflix and that opens up a VAST library of content.
http://www.roku.com/channels/#!browse/most-watched
That takes you to a page with a circular menu of about twenty-five pages of categories of channels, some free, some paid. Each channel has a description and an indication of the cost. Some are like hulu, free and premium.